Laminated stator cores, such as may be used in electric machines, may be formed by a plurality of laminations including a layer of insulating material located between adjacent laminations to prevent electrical conduction between the laminations. The laminated cores may be inspected for interlamination shorts during manufacture and during maintenance operations to identify conditions that may cause damage to the laminated core. The inspection operation may be performed using a measuring method comprising ring excitation of the stator lamination with a predetermined induction. This method, which indicates the effect of currents due to interlamination shorts by local temperature differences, requires a high-power and high-voltage source and excitation windings with large cross sections.
In another inspection technique, the laminated core may be provided with a special winding to excite magnetic flux in the overall core, and a low flux density is induced in the core. This inspection technique, known as an electromagnetic core imperfection detector (EL CID) test, provides a flux density in testing that is different than the flux density in operation of the electric machine, and may not provide sufficient flux to the laminated core teeth to provide a detection of insulation damage in the tooth area.